HK1148243A - Carbon fibers and films and methods of making same - Google Patents

Description

Carbon fibers and carbon films and methods of making the same

Cross reference to related applications

The present application claims the benefit of U.S. provisional patent application 60/979,146, filed on.10/11/2007, which is incorporated herein by reference as if fully set forth below.

Statement of federally sponsored research

The invention was made with U.S. government support (grant number FA9550-07-1-0233 awarded by air force scientific research institute). The U.S. government has certain rights in this invention.

Technical Field

Embodiments of the present invention generally relate to carbon fibers and carbon films, and more particularly, to carbon fibers and carbon films formed from acrylonitrile-containing polymers, and methods of making the same.

Background

Acrylonitrile-containing polymers are important industrial polymers for making fibers for use in fabrics, carpets and carbon fibers. Acrylic fibers produced from polyacrylonitrile copolymers are currently the dominant precursors for carbon fibers, in part because polyacrylonitrile-based carbon fibers exhibit good tensile and compressive properties.

Recently, methods have been developed to produce carbon nanotube-containing polymer composites, particularly carbon fibers containing Carbon Nanotubes (CNTs), wherein the CNTs are well dispersed in the composite. For example, U.S. patent No.6,852,410, which is incorporated herein by reference in its entirety as if fully set forth below, discloses such methods. Among other improvements, these methods provide composite fibers having higher tensile modulus and tensile strength. While new applications continue to emerge, there is a real need for improved materials.

Thus, there is a need for new carbon fibers and carbon films that exhibit higher tensile modulus and tensile strength. New methods for making carbon fibers and films are also needed. It is to the provision of such materials and methods that the various embodiments of the present invention are directed.

Disclosure of Invention

Embodiments of the present invention are directed to carbon fibers and carbon films, and methods of making the same. High strength and high modulus fibers and films may be used in a variety of applications including, but not limited to: reinforcement of materials (e.g., in tire cord and cement), aircraft parts, van bodies for high performance vehicles (e.g., F-1 racing cars and motorcycles), sports equipment (e.g., bicycles, golf clubs, tennis rackets, and sleds), and other demanding mechanical properties. Because of their electrical and thermal conductivity, these carbon fibers and carbon films also find various uses in electronic devices, fuel cells, electrochemical capacitors, and the like.

In general, methods of making carbon fibers according to embodiments of the present invention include extruding a solution of a first component and a solution of a second component through a bicomponent extrusion apparatus to form a bicomponent polymer fiber having the first component and the second component, and drawing the bicomponent polymer fiber to form a drawn bicomponent polymer fiber. The first component typically comprises an acrylonitrile-containing polymer. In some cases, extrusion may be accomplished using gel-extrusion or solution-extrusion.

The method can further include a process for stabilizing the drawn bicomponent polymeric fiber. The stabilization process may be accomplished under tension, and/or in an oxidizing environment, and/or at a temperature of from about 200 ℃ to about 400 ℃ for less than or equal to about 36 hours. The method can further include carbonizing the stabilized polymer fiber. The carbonization process can be accomplished under tension, and/or in an inert atmosphere, and/or maintained at a temperature of about 500 ℃ to about 1800 ℃ for less than or equal to about 2 hours. The method may further comprise graphitizing the carbonized polymer fiber. The graphitization process may be accomplished under tension, and/or in an inert environment other than nitrogen, and/or maintained at a temperature of 1800 c to about 2800 c for less than or equal to about 1 hour.

The process may also include separating the first component from the second component of the drawn or stabilized bicomponent polymeric fiber. The separation process may be accomplished by dissolving the second component from the drawn or stabilized bicomponent polymer fiber, sonicating the drawn or stabilized bicomponent polymer fiber to reduce any interfacial interactions between the first component and the second component, heating to melt the second component to leave the drawn or stabilized bicomponent polymer fiber, heating to burn the second component off to leave the drawn or stabilized bicomponent polymer fiber, or a combination comprising at least two of the foregoing processes. The stabilization process can also occur simultaneously with the separation process.

After drawing, the drawn polymer fibers have an average diameter of about 100nm to about 1 mm. The final carbon fibers have an average diameter of about 10nm to about 10 μm.

Various other embodiments of the present invention are directed to methods of making Carbon Nanotubes (CNTs) -containing carbon fibers or carbon films. The methods include contacting CNTs with an acrylonitrile-containing polymer to form a first component solution, extruding the first component solution with a second component solution to form a bi-component polymer-CNT fiber or film precursor comprising a first component and a second component, and stretching the bi-component polymer-CNT fiber or film precursor to form a drawn bi-component polymer-CNT fiber or film.

The methods can further include stabilizing the drawn bi-component polymer-CNT fiber or film, separating a primary component from a secondary component of the drawn or stabilized bi-component polymer-CNT fiber or film, carbonizing the stabilized polymer-CNT fiber or film, and/or graphitizing the carbonized polymer-CNT fiber or film. The electrical conductivity of the carbon fiber or carbon film produced by such a method is at least 25% higher than that of a carbon fiber or carbon film not containing CNT. The carbon fiber or carbon film produced by such a method has a tensile strength at least 0.5GPa higher than that of a carbon fiber or carbon film produced without the CNT. The carbon fiber or carbon film has a tensile modulus at least 50GPa greater than a tensile modulus of a carbon fiber or carbon film made without the CNT.

In certain particular embodiments, the CNTs can include single-walled nanotubes, double-walled nanotubes, triple-walled nanotubes, multi-walled (i.e., four or more walls) nanotubes, or a combination of two or more of the foregoing types of CNTs. In certain embodiments, the CNTs have an average diameter of about 0.5nm to about 25 nm. In other embodiments, the CNTs have an average diameter of less than or equal to about 10 nm. The CNTs can have an average length greater than or equal to about 10 nm. The CNTs may comprise from about 0.001 wt% to about 40 wt% of the bicomponent polymer-CNT fiber or film precursor. Also, the CNTs may comprise from about 0.001% to about 80% of the total weight of the final carbon fiber or carbon film.

The average diameter of the collectively drawn polymer-CNT fibers is about 100nm to about 1 mm. The average diameter of the final carbon fiber is about 10nm to about 10 μm. Also, the drawn polymer-CNT film has an average thickness of about 50nm to about 50 μm. The average thickness of the final carbon film may be about 25nm to about 25 μm.

In certain embodiments, the CNTs in the final carbon fiber or carbon film are collapsed. The carbon fiber or carbon film may have a region of microcrystalline graphite extending radially from about 0.34nm to about 50nm from one wall of each CNT. In certain embodiments, the microcrystalline graphitic region extends radially at least about 2nm away from the wall of each CNT.

Various other embodiments of the present invention are directed to methods of making carbon fibers or carbon films comprising graphite sheets. These methods comprise contacting graphite flakes with an acrylonitrile-containing polymer to form a first component solution, extruding the first component solution with a second component solution to form a bi-component polymer-graphite sheet fiber or film precursor comprising a first component and a second component, and stretching the bi-component polymer-graphite sheet fiber or film precursor to form a drawn bi-component polymer-graphite sheet fiber or film.

The methods can further include stabilizing the drawn bi-component polymer-graphite sheet fiber or film, separating a primary component from a secondary component of the drawn or stabilized bi-component polymer-graphite sheet fiber or film, carbonizing the stabilized polymer-graphite sheet fiber or film, and/or graphitizing the carbonized polymer-graphite sheet fiber or film. The electrical conductivity of the carbon fiber or carbon film produced by such a method is at least 25% higher than that of a carbon fiber or carbon film without graphite sheets. The carbon fiber or carbon film produced by such a method has a tensile strength at least 0.5GPa greater than that of a carbon fiber or carbon film produced without the graphite sheet. The carbon fiber or carbon film has a tensile modulus at least 50GPa greater than a tensile modulus of a carbon fiber or carbon film made without the graphite sheet.

In certain particular embodiments, the graphite flakes can have an average width of about 0.5nm to about 100 nm. In other embodiments, the graphite platelets have an average width of less than or equal to about 10 nm. The graphite flakes can have an average thickness of about 0.5nm to about 25 nm. The graphite flakes can have an average length of greater than or equal to about 10 nm. The graphite sheets can comprise from about 0.001% to about 40% by weight of the bi-component polymer-graphite sheet fiber or film precursor. Likewise, the graphite flakes can comprise from about 0.001% to about 80% of the total weight of the final carbon fiber or carbon film.

The drawn polymer-graphite sheet fibers may have an average diameter of about 100nm to about 1 mm. The average diameter of the final carbon fiber may be about 10nm to about 10 μm. Likewise, the drawn polymer-graphite sheet film can have an average thickness of about 50nm to about 50 μm. The average thickness of the final carbon fiber may be about 25nm to about 25 μm.

In certain embodiments, the graphite sheets in the final carbon fiber or carbon film are exfoliated. The carbon fiber or carbon film may have a region of microcrystalline graphite extending radially from about 0.34nm to about 50nm from one face of each graphite sheet. In certain embodiments, the microcrystalline graphitic region extends radially at least about 2nm away from the face of each graphite sheet.

Various other embodiments of the present invention are directed to carbon fibers or carbon films. Carbon fibers or carbon films can be formed from CNTs and an acrylonitrile-containing polymer. The carbon fibers may have an average diameter of about 10nm to about 10 μm; the carbon thin film may have an average thickness of about 25nm to about 25 μm. In some cases, the carbon fibers may have an average diameter of less than or equal to about 500nm, and the carbon film may have an average thickness of less than or equal to about 1 μm.

The microcrystalline graphitic region can be found in carbon fibers or carbon films to extend radially from about 0.34nm to about 50nm away from the wall of each CNT. In certain embodiments, the microcrystalline graphitic region extends radially at least about 2nm away from the wall of each CNT.

The carbon fibers or carbon films may have collapsed CNTs. The electrical conductivity of the carbon fiber or carbon film is at least 25% higher than that of those carbon fibers or carbon films that do not contain CNTs. Depending on the particular size of the fibers or films, they may be optically transparent in certain embodiments.

The tensile strength of the carbon fiber or carbon film may be at least 0.65GPa greater than that of a carbon fiber or carbon film formed without CNTs. The tensile modulus of the carbon fibers or carbon films is at least 75GPa greater than those of carbon fibers or carbon films formed without CNTs.

Still other embodiments of the present invention are directed to carbon fibers or carbon films. Carbon fibers or carbon films can be formed from graphite sheets and an acrylonitrile-containing polymer. The carbon fibers have an average cross-sectional dimension of about 10nm to about 10 μm; the carbon thin film has an average thickness of about 25nm to 25 μm. In some cases, the carbon fibers may have an average diameter of less than or equal to about 500nm, and the carbon film may have an average thickness of less than or equal to about 1 μm.

It can be found in carbon fibers or carbon films that the microcrystalline graphitic region extends radially from about 0.34nm to about 50nm away from one face of the graphite sheet. In certain embodiments, the microcrystalline graphitic region extends radially at least about 2nm away from one face of each graphite sheet.

The carbon fibers or carbon films may have collapsed graphite flakes. The electrical conductivity of the carbon fibers or carbon films may be at least 25% higher than those carbon fibers or carbon films that do not contain graphite sheets. Depending on the particular size of the fibers or films, they may be optically transmissive in certain embodiments.

The tensile strength of the carbon fibers or carbon films is at least about 0.65GPa greater than those formed without the graphite sheets. The tensile modulus of the carbon fibers or carbon films is at least about 75GPa greater than those formed without the graphite sheets.

Other aspects and features of embodiments of the present invention will become apparent to those ordinarily skilled in the art upon review of the following detailed description in conjunction with the accompanying figures.

Drawings

Fig. 1(a) and (b) are flow charts of processes illustrating methods of making carbon fibers or carbon films according to certain embodiments of the present invention.

FIG. 2 is a schematic illustration of a two-component extrusion apparatus according to certain embodiments of the present invention.

FIG. 3 is a schematic representation of the geometry of individual bicomponent fibers according to certain embodiments of the present invention.

Fig. 4 is a schematic of the geometry of each bicomponent film according to some embodiments of the invention.

FIG. 5 includes (a) high resolution transmission electron microscopy (HR-TEM) images and (b) Raman spectra of pristine CNTs.

Fig. 6 includes Scanning Electron Microscope (SEM) images showing separation of PAN/CNT island fibers from the PMMA marine component at (a) low magnification and (b) high magnification.

FIG. 7 is a schematic view of an apparatus for creating stress or tension in a fiber during stabilization and carbonization.

FIG. 8 includes stress-strain curves for carbonized PAN and PAN/CNT (99/1) fibers.

FIG. 9 includes the tensile strength of the carbonized PAN and PAN/CNT fibers as a function of fiber cross-sectional area.

Fig. 10 includes SEM images of fracture surfaces of (a) carbonized PAN island-type fibers and (b) carbonized PAN/CNT island-type fibers.

FIG. 11 includes HR-TEM images of (a) carbonized PAN and (b) - (d) carbonized PAN/CNT fibers.

FIG. 12 includes Raman spectra of carbonized island-type PAN and PAN/CNT (99/1) fibers.

Detailed Description

Exemplary embodiments of the present invention will now be described in detail with reference to the drawings, wherein like reference numerals represent like parts throughout the several views. Through this description, various components may be considered to have particular values or parameters, however, these are provided as exemplary embodiments. Indeed, the exemplary embodiments do not limit the various aspects and concepts of the invention, as many similar parameters, sizes, ranges, and/or values may be employed. The terms "first," "second," and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Furthermore, the terms "a," "an," and "the" are not intended to be limiting, but rather denote the presence of at least one of the referenced item.

The small diameter carbon fibers and the small thickness carbon films disclosed herein are formed from acrylonitrile-containing polymers. In addition, the carbon fibers and/or carbon films optionally may be formed from a composite comprising acrylonitrile-containing polymer and Carbon Nanotubes (CNTs). In other embodiments, the carbon fibers and/or carbon films optionally may be formed from composites comprising acrylonitrile-containing polymers and individual or groups of graphite sheets. Carbon fibers and/or carbon films obtained by incorporating CNTs and/or graphite flakes into precursors of carbon fibers and/or carbon films exhibit a number of beneficial properties, as described in more detail below.

The acrylonitrile-containing polymer described herein to produce a carbon fiber or carbon film of small size (i.e., small diameter or small thickness) may include a copolymer containing one acrylonitrile monomer and another (i.e., at least one other) monomer. Thus, the term "copolymer" also includes terpolymers and other polymers having more than two different monomers. Examples of acrylonitrile-containing polymers include, but are not limited to, Polyacrylonitrile (PAN), poly (acrylonitrile-methyl acrylate), poly (acrylonitrile-methacrylic acid), poly (acrylonitrile-acrylic acid), poly (acrylonitrile-itaconic acid), poly (acrylonitrile-methyl methacrylate), poly (acrylonitrile-itaconic acid-methyl acrylate), poly (acrylonitrile-methyl methacrylate-methyl acrylate), poly (acrylonitrile-vinyl pyridine), poly (acrylonitrile-vinyl chloride), poly (acrylonitrile-vinyl acetate), and combinations thereof.

The relative amounts of comonomers in the acrylonitrile copolymer, as well as the molecular weight of the acrylonitrile-containing polymer, depend on what properties the fiber or film is desired to have. Although different amounts can be used, it is desirable to add the acrylonitrile monomer in an amount greater than about 85 weight percent based on the total weight of the entire acrylonitrile-containing polymer. In addition, the molecular weight of the acrylonitrile-containing polymer is preferably in the range of about 50,000 g/mole to about 2,000,000 g/mole, and more desirably 100,000 g/mole to 500,000 g/mole, although other molecular weight ranges may be employed.

The carbon nanotubes used to make the small-sized carbon fibers or carbon films described herein can be any type of carbon nanotube, including single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), triple-walled carbon nanotubes (TWNTs), multi-walled carbon nanotubes (MWNTs), and the like, or a combination comprising two or more of the foregoing types of carbon nanotubes (e.g., a mixture of SWNTs and DWNTs, a mixture of DWNTs and TWNTs, SWNTs, a mixture of DWNTs and TWNTs, and the like). CNTs can be tubular or collapsed carbon nanotubes.

Carbon nanotubes can be made by any known method, including but not limited to vapor phase synthesis from high temperature, high pressure carbon monoxide, catalytic vapor deposition using carbonaceous feedstock and metal catalyst particles, laser ablation, arc process, or any other method of synthesizing carbon nanotubes.

The synthesized CNTs are usually in powder form, but may be used in an array form such as a felt form, a forest form, or a particulate form. The carbon nanotubes may have an average diameter of about 0.5nm to about 25nm, preferably about 0.5nm to about 10 nm. In some embodiments, it may be desirable to use carbon nanotubes having an average diameter of less than or equal to about 10 nm. The carbon nanotubes may have a length greater than or equal to about 10 nm. For example, carbon nanotubes having a length in millimeters or even centimeters may be used.

The purity of the CNTs is preferably at least 95%, and more preferably at least 99%, to minimize the potential for adverse effects caused by impurities remaining in the CNT sample. Thus, optionally, the CNTs can be purified to remove non-nanotube carbon, such as amorphous carbon, as well as residues of metal catalysts.

The purification process may employ any known method. The purification steps of carbon nanotubes are well known to those skilled in the art. Optionally, the cleaned CNTs may also be dried. Also, drying steps are well known to those skilled in the art.

Optionally, the CNTs may also be derivatized at their ends and/or sides with a functional group. These functional groups may include alkyl, acyl, aryl, aralkyl, halogen, substituted OR unsubstituted thiol, substituted OR unsubstituted amino, hydroxyl, OR ', wherein R' may include alkyl, acyl, aryl, aralkyl, substituted OR unsubstituted amino, substituted OR unsubstituted thiol, and halogen; or a linear or cyclic carbon chain, optionally interrupted by one or more heteroatoms, and optionally substituted by one or more ═ O or ═ S, hydroxyl, aminoalkyl, amino acid, or peptide. The degree of substitution can be designed to achieve the desired chemical effect, as will be appreciated by those skilled in the art. As an example, the number of carbon atoms in the alkyl, acyl, aryl, alkaryl groups may range from 1 to about 30.

Optionally, the CNT may further include a non-carbon element in its main chain. Depending on the specific use of the carbon fiber or the carbon thin film, for example, boron, nitrogen, sulfur, silicon, or the like may be included in the main chain of the CNT.

Also, the graphite sheets described herein for making small-sized carbon fibers or carbon films can be made by any known synthesis method. The graphite platelets may have an average width of about 0.5nm to about 100nm, preferably about 0.5nm to about 50 nm. In certain embodiments, it is desirable to use graphite flakes having an average width of less than or equal to about 10 nm. The graphite flakes can have an average length of greater than or equal to about 10 nm. For example, graphite sheets having a length in millimeters or even centimeters may be used. The graphite platelets may have an average thickness of about 0.5nm to about 25nm, desirably about 0.5nm to 10 nm. When multiple sets of graphite sheets are used to make small size carbon fibers or carbon films, there can be as many as 75 sheets of graphite in a set.

As with the way CNTs are processed, the graphite sheets are preferably purified to minimize the potential for adverse effects from impurities remaining in the graphite sheet sample. Like carbon nanotubes, the graphite sheets may be derivatized and/or contain non-carbon elements in the backbone. Optional derivatization and incorporation of non-carbon elements into the backbone can be performed to minimize aggregation of the graphite sheets in the carbon fiber or carbon film.

The small size of the carbon fibers and films can be achieved by preparing multicomponent or conjugated fibers or films, as described below, so that the desired small size of the fibers or films can be achieved. The use of multicomponent fiber or film processing overcomes the size limitation drawbacks of existing fiber or film processing equipment while providing the possibility of retrieving many small size fibers or films from a single multicomponent fiber or film.

Referring now to fig. 1(a) and (b), a process flow, generally designated 100, is shown representing the fabrication of small-size or small-thickness carbon fibers or carbon films, respectively, according to certain embodiments of the present invention. For simplicity, the process flow shown in FIGS. 1(a) and (b) refers to a two-component system. It should be understood that more than two components may be present in the multicomponent fiber or film. Thus, although reference is made to a second component, as shown in the figures and described below with respect to processing of the second component, processing of a third component, a fourth component, and so forth, is also contemplated.

Fig. 1(a) shows a process flow for making carbon fibers or carbon films from an acrylonitrile-containing polymer without CNTs or graphite sheets. Process 100 begins at 120 with two separate solutions, each independently containing a first component and a second component of a bicomponent fiber or film, sol extruded or solution extruded through a bicomponent extrusion device to form a bicomponent polymer fiber or film precursor. Process 100 may also include the preparation of first and second component solutions, depicted as 110 and 115, respectively; alternatively, the solution may be prepared in advance. The first component includes an acrylonitrile-containing polymer. The bicomponent polymer fiber precursor or polymer film precursor can then be stretched (as shown at 125) to form a drawn bicomponent polymer fiber or drawn polymer film, respectively.

Next, as shown at 130, the first component of the drawn bicomponent polymeric fiber or film can be separated from the second component of the drawn bicomponent polymeric fiber or film. After separation, the first component of the drawn bicomponent polymeric fiber or film may be heat stabilized as shown at 135. Finally, as shown at 140 and 145, the stabilized first component polymer fiber or film can be carbonized and graphitized, respectively, to form the final carbon fiber or carbon film.

Alternatively, the bicomponent polymer fiber or film may be heat stabilized (as shown at 135) after stretching (as shown at 125). Upon stabilization, the bicomponent fiber or film can be separated (as shown at 130). After the separation process 130, the first component of the bicomponent fiber or film may be carbonized (as shown at 140). Finally, after the carbonization process 140, the first component of the bicomponent fiber or film may be graphitized (as shown at 145).

As described in more detail below, the first component may also separate from the second component due to the temperature to which the bicomponent polymer fiber or film is subjected during the stabilization process 135. In these embodiments, the first component of the bi-component polymer fiber or film may be carbonized (as shown at 140) after the pulled bi-component polymer fiber or film stabilization process 135, without utilizing the actual separation step 130. Also, after the carbonization process 140, the first component of the bi-component fiber or film may undergo a graphitization process 145 to form a final carbon fiber or carbon film.

In typical embodiments, one or more of the sol-or solution-extrusion step 120, the stretching step 125, the separation step 130, the stabilization step 135, the carbonization step 140, and the graphitization step 145 are processes that are performed continuously, rather than batch-wise.

Fig. 1(b) shows a process flow for making carbon fibers or carbon films from a composite comprising acrylonitrile-containing polymer and CNT and/or graphite flakes. Although the process flow shown in fig. 1(b) refers only to CNTs, it is to be understood that graphite sheets may be used in place of, or in addition to, CNTs during practice. Thus, for example, when referring to stabilization process 135 of a drawn bi-component polymer-CNT fiber or film, a drawn bi-component polymer-graphite sheet fiber or film, or a drawn bi-component polymer-CNT/graphite sheet fiber or film, can also be stabilized by stabilization process 135 under the process conditions shown in the figures and below.

The process 100 shown in fig. 1(b) begins at 120 with two separate solutions, each independently containing a first component and a second component of a bicomponent fiber or film, being extruded through a bicomponent extrusion apparatus to form a bicomponent polymer-CNT fiber or film precursor. Process 100 may also include the preparation of first and second component solutions, depicted as 110 and 115, respectively; alternatively, the solution may be prepared in advance. The first component of the scheme includes acrylonitrile-containing polymers and CNTs (whether synthesized, purified, or derivatized). The solution of the first component is prepared by contacting CNTs with an acrylonitrile-containing polymer. The solution can be considered a polymer-CNT dopant. The bi-component polymer-CNT fiber or film precursor is then drawn (as shown at 125) to form a drawn bi-component polymer-CNT fiber or film, respectively.

Variations of the flow sequence shown in fig. 1(a) are equally applicable to the process 100 shown in fig. 1 (b). Thus, after the stretching step 125, the process 100 may proceed to a separation step 130, a stabilization step 135, a carbonization step 140, and a graphitization step 145; a stabilization step 135, a separation step 130, a carbonization step 140, and a graphitization step 145; alternatively, the stabilization step 135, the carbonization step 140, and the graphitization step 145. As with the flow chart shown in fig. 1(a), in typical embodiments, one or more of the extrusion step 120, the stretching step 125, the separation step 130, the stabilization step 135, the carbonization step 140, and the graphitization step 145 are processes that are performed in series.

The purpose of the process shown in fig. 1(a) and 1(b) is to produce carbon fibers or carbon films of small size or small thickness, respectively. It should be recognized, however, that extremely fine microfibers or films having these small dimensions or small thicknesses, respectively, may be collected from the process of the stretching step 125 or the stabilization step 135. Thus, for these embodiments, the processes do not include at least the carbonization step 140 and the graphitization step 145.

Hereinafter, each process step will be described with reference to the flow shown in fig. 1 (b). However, it should be understood that the steps described below apply equally to the flow scheme shown in FIG. 1(a) (i.e., carbon fibers or carbon films made using acrylonitrile-containing polymers without CNTs and/or graphite sheets) without departing from the details and parameters provided below, except for step 110, which is the step of preparing the first component solution. Thus, for example, when referring to a stabilization step 135 of a drawn bi-component polymer-CNT fiber or film, a drawn bi-component polymer (without CNT and/or graphite sheets) fiber or film may also be stabilized via step 135 under general conditions encompassed by the parameters described below. It should also be understood that any reference to the number, ratio, etc. of CNTs is intended only to refer to the flow shown in figure 1 (b). For the sake of brevity (i.e., to minimize repetition of text, process steps, conditions, amounts, proportions, etc. with respect to the CNTs are not described again with respect to graphite sheets), it should be understood that all references to CNTs, by extension, are meant to include graphite sheets, whether used as a substitute for CNTs or in combination with CNTs.

The first component solution is prepared by contacting the CNTs with an acrylonitrile-containing polymer, and to accomplish this step 110, the CNTs (extended, and/or graphite flakes) are first dispersed in a solvent, followed by the addition of the acrylonitrile-containing polymer. Alternatively, the CNTs and the acrylonitrile-containing polymer can be mixed in the solvent at the same time (i.e., not stepwise). It is also possible to use a method in which the acrylonitrile-containing polymer is dispersed in a solvent, followed by the addition of CNTs, which may be dry or already dispersed in the same or a different solvent. In yet another alternative, CNTs can be combined with acrylonitrile-containing polymers in a melt. It is also possible to add dry CNTs or CNTs in solution to the acrylonitrile-containing polymer, which is in the monomer phase, or in any phase of the polymerization reaction, which results in the formation of the acrylonitrile-containing polymer.

The solvent is preferably capable of solubilizing (i.e., at least partially dissolving) the CNT and the acrylonitrile-containing polymer. Dimethylformamide (DMF) and dimethylacetamide (DMAc) are typical solvents that may be used to suspend or solubilize polyacrylonitrile polymers and copolymers. Other examples of organic solvents that may be used to suspend or solubilize the polyacrylonitrile polymers and copolymers include, but are not limited to, dimethyl sulfoxide (DMSO), ethylene carbonate, propylene carbonate (dioxanone), chloroacetonitrile, dimethyl sulfone, propylene carbonate, malononitrile, succinonitrile, adiponitrile, γ -butyronitrile, acetic anhydride, epsilon-caprolactam, bis (2-cyanoethyl) ether, bis (4-cyanobutyl) sulfone, chloroacetonitrile/water, chloroacetonitrile, cyanoacetic acid, dimethyl phosphate, tetramethylene sulfoxide, glutaronitrile, succinonitrile, N-formylhexamethyleneimine, 2-hydroxyethylmethyl sulfone, N-methyl- β -cyanoethylformamide, methylene dithiocyanate, N-methyl- α, α, α, -trifluoroacetamide, 1-methyl-2-pyridone, 3, 4-nitrophenol, nitromethane-Water (94: 6), N-nitrosopiperidine, 2-oxazolidinone, 1, 3, 3, 5-tetracyanopentane, 1, 1, 1-trichloro-3-nitro-propane and p-phenol-sulfonic acid. Examples of inorganic solvents include, but are not limited to, aqueous concentrated acids, such as concentrated nitric acid (about 69.5 wt.% HNO)₃) Concentrated sulfuric acid (about 96 wt% H)₂SO₄) Etc.; concentrated salt solutions, e.g. ZnCl₂LiBr, NaSCN and the like.

Mixing techniques or methods for dispersing the nanotubes and/or acrylonitrile-containing polymer in the solvent include, but are not limited to, sonication (i.e., using an ultrasonic bath or an ultrasonic head), homogenization (e.g., using a biological homogenizer), mechanical stirring (e.g., using a magnetic stir bar), high shear mixing methods, extrusion (e.g., single or multiple screw extruders), and the like. In certain embodiments, heat can be used to facilitate dispersion of the CNTs and/or acrylonitrile-containing polymer in the solvent. Generally, heating to the boiling point of the solvent is possible.

The mixing time depends on various parameters including, but not limited to, the solvent, the temperature of the mixture, the concentration of the nanotubes and/or acrylonitrile-containing polymer, and the mixing technique. Mixing time is the time required to prepare a generally uniform suspension or dispersion.

After dispersing the CNTs and/or acrylonitrile-containing polymer in a selected solvent to form a suspension, some of the solvent may optionally be removed. The solvent may be removed by any known method, such as heating, vacuum, evaporation of the solvent at ambient conditions, and the like. The time and temperature required to adjust the concentration of solvent in the suspension depends on various parameters including, but not limited to, the particular solvent employed, how much solvent is to be removed, and the nature of the solvent.

The concentration of the acrylonitrile-containing polymer in a particular solvent depends on various factors, one of which is the molecular weight of the acrylonitrile-containing polymer. The concentration of the polymer solution is selected to provide a viscosity that allows extrusion of the selected fiber or film with a desired result. Generally, with respect to the preparation of polymer solutions, the polymer molecular weight is inversely related to the polymer concentration. In other words, the higher the molecular weight of the polymer, the lower the concentration of the polymer to obtain a desired viscosity. For example, in DMF or DMAc, where the molecular weight of the acrylonitrile-containing polymer is on the order of about 50,000 g/mole, solution concentrations as high as about 25 weight percent can be achieved; solution concentrations as high as about 15% by weight can be achieved with acrylonitrile-containing polymers having molecular weights on the order of about 250,000 g/mole; on the order of molecular weight of acrylonitrile-containing polymers of about 1000,000 g/mole, solution concentrations as high as about 5% by weight can be achieved. The concentration of the solution may also be affected by, among other variables, the particular polymer composition, the particular solvent, and the solution temperature.

When the acrylonitrile-containing polymer is added to the nanotube-solvent suspension, it is homogenized to form an optically homogeneous polymer-CNT solution or suspension, also referred to as a "dope". The acrylonitrile-containing polymer can be added all at once, continuously in stages, or in stages to give a generally homogeneous solution. The polymers may be mixed to produce an optically homogeneous solution using any technique, such as mechanical agitation, sonication, homogenization, high shear mixing, extrusion, or combinations thereof.

Also, when the CNT and the acrylonitrile-containing polymer are mixed together with the solvent at the same time, the three components mix to form an optically uniform polymer-CNT dopant. The nanotubes and polymer can be mixed using any technique, such as mechanical agitation, sonication, homogenization, high shear mixing, extrusion, or combinations thereof, to produce an optically homogeneous solution.

Generally, the nanotubes will constitute from about 0.001 wt% to about 40 wt% of the dopant, with from about 0.01 wt% to about 5 wt% being desirable.

There is no particular limitation in selecting the second component of the two-component system. Generally, the second component is selected so that it can be extruded and drawn together with the first component, but separated from the first component in any of a number of ways, as will be described below. Therefore, the second component polymer should not be crosslinkable with the acrylonitrile-containing polymer of the first component. Factors that may influence the choice of the second component polymer include viscosity, melting temperature, compatibility with the acrylonitrile-containing polymer, rheological properties, and the like. For example, the viscosity values of the two polymer components should be similar. Otherwise, the higher viscosity component resists rearrangement during the extrusion step, causing a distortion in the distribution of the component across the fiber or film section. Also, when using heating means to separate the two components of a bicomponent fiber or film, the melting point of the second component polymer should not be substantially similar to the melting point of the acrylonitrile-containing polymer of the first component, as it may complicate the separation process. The actual choice of the second component polymer will not be difficult for the skilled person.

The method of preparing the solution of the second component may include dispersing or dissolving the second component polymer in a solvent. The solvent is preferably capable of solubilizing the second component polymer. In typical embodiments, the solvent is the same as the solvent used to prepare the first component solution.

After the first component solution and the second component solution are prepared, the two solutions are formed into a polymer-CNT fiber or film by a co-extrusion step 120. The term "extrusion" as used herein is meant to generally include not only the stretching process used to make stretchable bicomponent films, but also the spinning process used to make stretchable bicomponent fibers. The extrusion step 120 can be accomplished by any method for making a stretchable fiber or film. Examples of suitable methods for forming stretchable fibers or films include, but are not limited to, gel extrusion (which includes gel spinning), wet extrusion (which includes wet spinning), dry extrusion (which includes dry spinning), dry-jet wet extrusion (which includes dry-jet wet spinning), electroextrusion (which includes electrospinning), melt extrusion (which includes melt spinning), and the like. When extruding a film, a slot die is used. After the component solutions are extruded through a multi-orifice spinneret or die, the fibers or films are respectively drawn through step 125 in a manner compatible with the extrusion technique employed.

In a typical embodiment, the technique used to extrude the solution of components is gel extrusion. It will be readily understood by those skilled in the art that the polymer concentration, solvent concentration, gelling medium, and gelling time can be varied to achieve the desired characteristics of the drawn fiber or film.

The extrusion step 120 is accomplished by using a two-component extrusion apparatus. Fig. 2 provides a schematic diagram of such an apparatus, generally designated 200. As shown, the solutions of the components are introduced separately into the apparatus 200. The individual solutions may be stored in a chamber that may optionally be heated to achieve the desired rheological properties of the solution of each component. Each solution may be passed through a filter to minimize the possibility of impurities remaining in the extruded bicomponent fiber or film. After passing through the filter, the solutions of the components are fed, if necessary, into a device for controlling the distribution or flow path of each solution. The solution of each component is then passed through a multi-orifice spinneret or die to produce a bi-component polymer-CNT fiber or film.

Many extruded bicomponent polymer-CNT fiber or film geometries can be obtained. Fig. 3 and 4 show representative, non-limiting sets of geometries for fibers and films, respectively. The geometry shown in fig. 3 includes so-called "sea-island type", "core-sheath type", "side-by-side type", "lamination type", and "mosaic type". The geometry shown in fig. 4 includes the so-called "core-sheath type" and the "side-by-side type".

The desired specific geometry can be produced by designing the device to control the distribution or flow path of each solution into the multi-orifice spinneret or die. Such devices are well known and commercially available and typically comprise one or more distributor plates having distributor flow paths etched into one or both faces of the plate to distribute the polymer components to the appropriate position of the multi-orifice spinneret or die inlet orifices. The distribution path may be sufficiently small to facilitate the creation of multiple discrete streams of the polymer component, parallel to the axis, into each of the multiple orifice spinneret or die orifice inlet orifices, so that the resulting extruded fiber or film can have a desired geometry. Specific examples of such devices can be found in U.S. Pat. Nos. 5,162,074, 5,344,297, 5,466,410, 5,533,883, 5,551,588, 5,575,063, 5,620,644, etc., all to BASF corporation, and U.S. Pat. Nos. 5,462,653, 5,562,930, all to Hills, Inc., all to Hills, Inc.

After extrusion step 120, the bi-component polymer-CNT fiber or film may be drawn via step 125. The diameter or thickness of the drawn fully bi-component polymer-CNT fiber or film (i.e., comprising the first component and the second component) can be controlled by the size of the pores of a multi-orifice spinneret or die, respectively. These diameters or thicknesses may also be controlled by the number of first components within the fiber or film. The drawn bicomponent polymer-CNT fibers may have an average diameter of about 100nm to about 1 mm. More specifically, the drawn bicomponent polymer-CNT precursor fiber can have an average diameter of about 100nm to about 100 μm. Similarly, the drawn bi-component polymer-CNT film precursor can have an average thickness of about 50nm to about 500 μm. More specifically, the drawn bi-component polymer-CNT precursor film can have an average thickness of about 100nm to about 100 μm. In drawn bicomponent polymer-CNT fibers or films, the CNTs can be tubular, or they can be flat or collapsed. In certain embodiments, particularly where the CNTs have an average diameter of less than or equal to about 15nm, the flattened or collapsed CNTs can become spread or unfolded into a shape, thus a graphite sheet having a width of about 0.5nm to about 100 nm.

All drawn bicomponent polymer-CNT fibers or films have satisfactory properties by themselves. For example, the drawn bi-component polymer-CNT fiber or film can have a tensile strength of about 0.25GPa to about 2 GPa. In some cases, the tensile strength may be at least 1 GPa. The drawn bicomponent polymer-CNT fiber or film can also have an initial tensile modulus of from about 15GPa to about 30 GPa; in some cases, the tensile modulus may be at least up to about 25 GPa. The drawn bicomponent polymer-CNT fiber or film may have a crystallinity of at least about 50%, and in some cases, at least up to 70%. Finally, the drawn bicomponent polymer-CNT fibers or films have a molecular orientation of at least about 0.75, and some fibers or films have a molecular orientation of at least up to about 0.9.

After the stretching step 125, the drawn bi-component polymer-CNT fiber or film may be subjected to one of two-step processes. The drawn bicomponent polymer-CNT fiber or film may be subjected to a separation step 130, or the drawn bicomponent polymer-CNT fiber or film may be subjected to a thermal stabilization step 135.

In the separation step 130, a first component comprising CNTs and an acrylonitrile-containing polymer is separated from a second component of the drawn bi-component polymer-CNT fiber or film. The separation can be achieved by dissolving the second component by chemical treatment, by sonication if the interface between the first and second components is poor, by mild heat treatment to melt the second component, by more intense heat treatment to burn the second component, etc. After the separation step 130, the first component of the drawn bi-component polymer-CNT fiber or film can undergo step 135 to be stabilized or step 140 to be carbonized (if it has been previously stabilized via step 135).

The stabilization step 135 generally comprises a heat treatment wherein the drawn polymer-CNT fibers or films, whether or not they have been separated, optionally may be placed under stress or tension. The heat treatment process takes place in an oxidizing atmosphere. During this oxidative stabilization, the acrylonitrile-containing polymer of the first component undergoes a chemical change, resulting in an increase in its density. It is believed that in certain embodiments, the stabilization process results in crystallization of the acrylonitrile-containing polymer, resulting in a material referred to as a "ladder polymer". In addition, some hydrogen evolution and/or oxygen absorption may occur.

Generally, the stabilization step 135 is carried out in air at a temperature of about 200 ℃ to about 400 ℃ and may last up to 36 hours, preferably about 30 seconds to about 24 hours. The exact stabilization and residence time depends in part on the composition of the acrylonitrile-containing polymer, the drawn polymer-CNT fiber diameter or film thickness, and whether the second component has been previously separated off. In certain embodiments, the heat treatment may be performed in multiple steps.

The stabilized first component of the bicomponent fiber or film may then be subjected to a separation step 130 or a carbonization step 140. The carbonization step 140 typically involves a heat treatment process in an inert environment (e.g., nitrogen, helium, argon, etc.) at a temperature higher than the temperature of the stabilization process. This step may be performed under tension or stress conditions with the stabilized first component fiber or film. During the carbonization step 140, the stabilized first component fiber or film has an increased carbon content (e.g., greater than 90 weight percent) to form a three-dimensional carbon structure. This generally occurs by pyrolysis.

Generally, the carbonization step 140 is performed at a temperature of about 500 ℃ to about 1800 ℃. May last up to 2 hours, preferably from about 1 millisecond to about 60 minutes. The exact stabilization and residence time will depend in part on the composition of the acrylonitrile-containing polymer, as well as the concentration of the CNTs in the composition. For example, higher charring temperatures can be used to increase modulus. In certain embodiments, the heat treatment may be performed in multiple steps.

After the carbonization step 140, the first component of the bicomponent fiber or film may undergo a graphitization step 145. The graphitization step 145 generally comprises a heat treatment process in an inert environment at a higher temperature than the carbonization process. Nitrogen is not used in the graphitization step 145 because nitrogen can react with carbon to form nitrides. This step may be performed under tension or stress conditions with the carbonized first component fiber or film.

Generally, the graphitization step 145 is performed at a temperature of about 1800 c to about 2800 c. May last up to about 1 hour, preferably from about 1 millisecond to about 15 minutes. The exact temperature and residence time will also depend in part on the composition of the acrylonitrile-containing polymer, as well as the concentration of the CNTs in the composition. In certain embodiments, the heat treatment may be performed in multiple steps.

Reference will now be made to the resulting carbon fibers and films containing CNTs and/or graphite flakes. As previously mentioned, it should be understood that for simplicity and to minimize repetition of the text, all references to CNTs, by extension, are meant to include graphite sheets, whether used as a replacement for CNTs or in combination with CNTs. In some cases, for clarity, similar conditions/properties are mentioned for the graphite sheets in the first description and are not repeated in the remaining text.

The average diameter of the final carbon fiber is typically about 10nm to about 10 μm. More specifically, they may have an average diameter of about 12nm to about 5 μm. The average thickness of the final carbon film is typically about 25nm to about 25 μm. More specifically, they have an average thickness of about 50nm to about 5 μm. The width of the film is not particularly limited. Depending on the particular size of the fiber or film, the film or fiber may be optically transparent. CNTs are present in the final carbon fiber or carbon film in an amount of about 0.001 wt% to about 80 wt%, preferably about 0.01 wt% to about 5 wt%.

In typical embodiments, the CNTs in the final carbon fiber or carbon film are collapsed. That is, CNTs are generally not seen to exist as large bundles or ropes of CNTs; the graphite sheets are generally not visible as an overlapping stack of sheets. More specifically, in these embodiments, the CNTs (and/or graphite sheets) are present in the final carbon fiber or carbon film as individual nanotubes (and/or graphite sheets) or as groups (and/or stacks) of on average less than 10 nanotubes (and/or graphite sheets) per group. In certain embodiments, each group averages less than 5 nanotubes. In further embodiments, less than 3 nanotubes per group are observed. Without being bound by theory, it is believed that collapsing of the nanotubes proceeds in different ways. It has been found that increasing the concentration of nanotubes results in more bundling in the final carbon fiber or carbon film. Thus, lower concentrations of CNTs can be employed to achieve collapse of the nanotubes. In addition, during the stretching step 125, regular or continuous stretching is believed to result in better collapse of the CNTs. For example, mixing a dilute dispersion (e.g., 10 milligrams of small diameter CNTs in 300 milliliters of solvent) with an acrylonitrile-containing polymer in solution preparation step 110, followed by regular stretching in stretching step 125, can result in CNTs in carbon fibers that are individually present or are present in groups averaging less than 3 nanotubes.

One advantageous feature of the process flow disclosed herein is that the graphitization step 145 is not necessary. In fact, even without the graphitization step, the CNTs present in the acrylonitrile-containing polymer induce graphitization at the lower temperature of the carbonization step 140. Specifically, after carbonization, a region of microcrystalline graphite was observed to extend radially from the wall of each CNT by about 0.34nm to about 50 nm. In the case of a graphite sheet, the region of microcrystalline graphite may extend directly from about 0.34nm to about 50nm away from one face of the graphite sheet. More generally, the microcrystalline graphitic region extends radially (and/or directly) about 1nm to about 30nm from the wall (and/or surface) of each CNT (and/or graphite sheet). In some cases, the microcrystalline graphitic region extends radially at least about 2nm away from the wall of each CNT. In other words, the effect of 1 wt% of the CNTs present in the polymer-nanotube mixture on the polymer surrounding the CNTs increased their reactivity by about 30%. These results are quite surprising given the lower temperature of the carbonization step 140 of the process flow of the present invention.

In addition, tension is applied to the fiber or film during one or more of the stabilization, carbonization, and optional graphitization steps, which is believed to also aid in the crystallization of the graphitic region surrounding the CNTs. Thus, in typical embodiments, tension is applied to the fiber or film during each of these steps.

Another advantageous feature of the process flow disclosed herein is that the drawn fiber or film is stabilized and carbonized (and optionally graphitized) such that the carbon fibers and carbon films produced have an increased tensile modulus and tensile strength. Generally, the addition of about 1 wt% CNT to a polymer-nanotube mixture can increase the tensile strength by at least 0.5GPa and the tensile modulus by at least 50GPa, as compared to a carbon fiber or carbon film prepared using the same preparation procedure but without any CNT. For fibers or films, an increase of at least 50% in tensile strength and/or tensile modulus can be achieved by adding about 1% by weight of CNTs to a polymer-nanotube mixture (still compared to a carbon fiber or carbon film prepared with the same preparation steps but without any CNTs).

The final carbon fiber or carbon film may have a tensile strength of up to about 10GPa or greater and a tensile modulus of up to about 750GPa or greater. For example, carbon fibers carbonized without a graphitization step made from PAN and CNT by gel extrusion may exhibit a tensile strength of up to about 6GPa, and a tensile modulus of up to about 600 GPa. Carbon fibers or carbon films can also be made with higher compressive strength than tensile strength.

It has also been observed that another improvement in the carbon fibers or carbon films produced by the present invention includes an improvement in electrical conductivity. The electrical conductivity of the carbon fiber or carbon film produced using the process flow described herein is improved by at least about 25% as compared to a carbon fiber or carbon film without any CNTs. In one embodiment, the conductivity is increased by more than 50%. In certain embodiments, the conductivity is 2 times or more, 5 times or more, or even 10 times or more, as compared to a carbon fiber or carbon thin film without any CNTs.

Various embodiments of the present invention will be further illustrated with reference to the following non-limiting examples.

Examples

Example 1: sea-island type bicomponent fiber

In this example, a sea-island bicomponent cross-sectional geometry and gel spinning process were used to produce small diameter Polyacrylonitrile (PAN) and PAN/Carbon Nanotube (CNT) composite fibers having about 99 wt% PAN and about 1 wt% CNT (99/1). Next, the sea component polymer is removed in a stabilization stage by complete thermal degradation, and the island-type component is stabilized and carbonized to obtain PAN and PAN/CNT-based carbon fibers having an effective diameter of about 1 μm or less. As will be described in more detail in this example, PAN/CNT (99/1) -based carbon fibers processed in this manner exhibited a tensile strength of about 4.5GPa (2.5N/tex) and a tensile modulus of about 463GPa (257N/tex), while the values for control PAN-based carbon fibers processed under the same conditions were about 3.2GPa (1.8N/tex) and about 337GPa (187N/tex), respectively. The properties of these small diameter carbon fibers were also compared to PAN and PAN/CNT-based carbon fibers of larger diameter (i.e., greater than about 6 μm).

The viscosity average molecular weight of PAN is about 250,000 g/mole, and is available from Eikeliman (Exlan) Co., Ltd. Carbon nanotubes (Lot # XO-021UA) were obtained from Houston (unitym) ltd (Houston, TX) and the CNTs used in this study contained about 1.6 wt% of catalytic impurities according to thermogravimetric analysis (TGA) in air. As shown in FIG. 5(a), high resolution Transmission Electron microscopy (HR-TEM) revealed that the CNT was a mixture of double-walled and triple-walled carbon nanotubes, with few multi-walled carbon nanotubes. As shown in fig. 5(b), the raman spectrum of the CNT has no radial ventilation mode. Poly (methyl methacrylate) (PMMA) has a molecular weight of about 85,000 to 150,000g/mol, available from Sellor Industries (Cyro Industries) (Orange, CT), and is used as the sacrificial "marine" component. Dimethylformamide (DMF) was obtained from Sigma-Aldrich.

The CNTs were dispersed in DMF at a concentration of about 40mg/L at room temperature using sonication (Branson)3510R-MT, 100W, 42kHz) for about 24 hours. About 14.85 grams of PAN was dissolved in about 100mL of DMF at about 80 ℃. To this PAN/DMF solution was added an optically homogeneous CNT/DMF dispersion. Any excess solvent was evaporated by vacuum distillation at about 80 ℃ while stirring to give the desired solution concentration (about 15 grams of solid per 100 milliliters of solvent). The solution of marine component is prepared by dissolving about 55 grams of PMMA in about 100ml of DMF at about 150 ℃.

Sea-island fibers were prepared by processing with a spinneret having a diameter of about 250 μm. The bicomponent filament drawing device is designed similar to that depicted in fig. 2. The temperature of the two solution tanks (i.e., the "island" tank containing PAN or PAN/CNT, the "sea" tank containing PMMA) was maintained at about 120 deg.c and the spinneret temperature was maintained at about 140 deg.c. The volume flow of the marine component and the island component is about 1.5cm³Min, which corresponds to a linear jet velocity of 61m/min, depending on the diameter of the spinning nozzle. The solution was drawn into a methanol bath maintained at about-50 ℃. The air gap between the spinneret and the methanol bath was maintained at about 5 cm. The drawn fibres (as-spun fibers) were collected at a speed of about 200m/min and immersed for several days in a methanol bath at about-50 ℃ to ensure gelling of the island-type components.

The gel bicomponent fiber is drawn in several stages at about 110 c, about 150 c, and about 170 c using an in-line heater. The draw ratio of PAN and PAN/CNT gel fibers to PMMA marine component was about 10. This does not include a draw ratio of 3.3 in the methanol bath during the drawing step.

The drawn fiber was then vacuum dried at about 70 ℃ for about 3 days. FIG. 6 gives a Scanning Electron Microscope (SEM) image of a precursor islands-in-sea fiber with and without separation of the marine component. The PMMA marine component can be removed by dissolution in nitromethane.

The dried sea-island precursor fiber (not having the marine component PMMA removed) was stabilized in a box furnace (Lindberg, 51668-HR box furnace 1200C, Blue M electricity) as shown in fig. 7, with the fiber hung on a quartz rod in air using two clamping steel blocks. An initial stress of 10MPa was applied depending on the cross-sectional area (PAN or PAN/CNT) of the island-type fiber. The fiber was heated in air from room temperature to about 285 c at a heating rate of about 1 c/min and held at about 285 c for about 4 hours. Subsequently, the mixture was heated to about 330 ℃ at a heating rate of about 1 ℃/min, and maintained at about 330 ℃ for about 2 hours. The stabilized fiber was then cooled to room temperature over several hours. During this stabilization, the marine component (PMMA) is completely burnt off.

Then, the stabilized island-type PAN and PAN/CNT fibers were heated from room temperature to about 1200 ℃ at a heating rate of about 5 ℃/min in an argon atmosphere, and were kept at about 1200 ℃ for about 5 minutes.

Tensile testing was performed on multifilament samples. The samples were prepared and tested using an RSA III solid analyser (Rheometric Scientific) with a gauge length of about 6mm and a crosshead extrusion speed of about 0.1%/s. The data were not corrected for mechanical compliance (machine compliance). The tensile rupture specimen was sputter-coated with gold and examined by SEM (LEO 1530, operating conditions: 10kV) to determine the effective cross-sectional area. To further ensure the accuracy of the cross-sectional area measurements, the SEM was calibrated with a standard sample (301BE, EMS, Hatfield, Pa.). The cross-sectional area of the fibers was determined using image analysis software (UTHSCSA image tool version 3.0, texas university health center, San Antonio, TX).

A wide angle X-ray diffraction (WAXD) pattern of the multifilament bundle was obtained using a Rigaku MicroMax-002 diffractometer (X-ray wavelength, λ ═ 0.15418nm) equipped with a rigoku R-axis IV + + detection system. Diffraction patterns were analyzed using AreaMax V.1.00 and MDI Jiade (Jade) 6.1. The orientation (f) of the carbonized graphite structure was measured₀₀₂) And crystal size (L)₀₀₂And L₁₀). Raman spectra of the carbonized fibers in backscattering geometry were collected using a hollep wave Research 785 raman microscope (Kaiser optical system) with 785nm excitation laser, equipped with a polarizer and analyzer parallel to each other, vv mode. The fiber was placed in a position parallel to the polarizer and analyzer in the raman microscope.

HR-TEM was performed using a JEOL 4000EX transmission electron microscope (operating voltage 400 kV). Carbon fiber samples for HR-TEM analysis were prepared by grinding the fibers with a jade mortar and pestle. The milled fibers were placed in ethanol and sonicated for about 15 minutes to further break up the fiber pieces into fine pieces. A drop of this dispersion was placed on a TEM grid (Electron microscopy sciences, Cat. #200C-LC) and dried for analysis.

Table 1 lists the tensile properties of the carbonized island-type PAN and PAN/CNT (99/1) fibers. For comparison, the tensile properties of larger diameter carbon fibers made from gel-spun PAN-based and PAN/CNT-based fiber processing are also listed in table 1. FIG. 8 is a representative stress-strain curve for carbonized PAN and PAN/CNT island fibers.

As shown in fig. 9, the tensile strength of PAN-based and PAN/CNT-based carbon fibers having different cross-sectional areas indicates that the strength is improved as the cross-sectional area is reduced. The data confirm two points: (a) a cross-sectional area, a tensile strength of a PAN/CNT-based carbon fiber having about 1 wt% CNTs in the precursor is about 25% to about 60% higher than a tensile strength of a corresponding PAN-based carbon fiber, and (b) the tensile strength increases with decreasing cross-sectional area.

TABLE 1 tensile Properties of carbonized island and Large diameter PAN and PAN/CNT (99/1) fibers

The precursor fiber had a diameter of about 12 μm

Precursor fiber diameter

About 20 μm

The tensile modulus of PAN-based carbon fibers increases monotonically with carbonization temperature, while the tensile strength reaches a maximum at about 1500 ℃. The modulus of the small diameter carbonized gel-spun PAN fiber is higher than commercially available fibers carbonized at the same temperature. The modulus of the corresponding PAN/CNT-based carbon fiber is much higher. These trends can be seen from table 1. It represents contributions from gel spinning, CNTs, and small fiber cross-sectional area.

One advantage of PAN-based carbon fibers over pitch-based carbon fibers or all CNT carbon fibers is compressive strength. Both the tensile strength and the compressive strength of PAN-based carbon fibers are high, and therefore these are the only carbon fibers used in structural composites, since compressive strength is also a necessary condition for structural composites. The recoil test (recoil test) as described in Kozey et al (Material 2. comprehensive properties of high Performance Fibers ("Compressive Fibers of materials2.high-Performance Fibers"), 1995, Journal of materials research (Journal of materials research, 10, 1044) can give an indirect measure of the Compressive strength of an elastic fiber. When an elastic fiber breaks in tension, it also breaks in compression if its tensile strength is higher than its compressive strength. The tensile stress wave propagates through the fiber to the clip, bouncing like a compression stress wave. If there is no energy loss in the fiber, the intensity of the compressive stress wave is the same as that of the tensile stress. Approximately 50% of the small diameter carbon fibers processed from gel-spun PAN/CNT fibers did not break under compression, but broke under tension. These observed phenomena suggest that the compressive strength of carbon fibers made from small diameter gel-spun PAN/CNTs is comparable to or higher than their tensile strength.

CNT-containing carbon fibers were along the fiber axis (L) as compared to carbonized control PAN fibers₁₀) More or less with smaller d-spacings and larger crystal sizes. This is confirmed by the data in table 2. The fractured surface of the PAN/CNT-based carbon fiber shows fibrils with diameters of about 20nm to about 50nm, which can be seen in fig. 10 (b). These fibrils indicate that PAN has graphitized around the CNTs. As seen in FIG. 10(a), the fracture behavior of the small diameter gel-spun PAN is that of PAN-based carbon fibersThe characteristics of (1).

TABLE 2 structural parameters of island fibers that have been carbonized

	Carbonized island-type PAN	Carbonized island type PAN/CNT (99/1)
			d-spacing(002)(nm)	0.357	0.356
L(002) a(nm)	1.3	1.3
			L(10) b(nm)	1.8	2.1

a crystal size from same distance scanning

b crystal size from tangential scanning

FIG. 11 includes HR-TEM images of carbonized PAN and PAN/CNT fibers. Although the carbonized PAN fibers shown in fig. 11(a) exhibit a lower ordered carbon structure, the fibril structure in the carbonized PAN/CNTs shown in fig. 11(b) -11(d) reveals a highly ordered graphitic structure. However, PAN/CNT-based carbon fibers do not merely add CNT to the carbonized PAN. In contrast, the presence of CNTs affects the charring of the PAN. The stabilization and charring of PAN immediately around CNTs is different from that of PAN far from nanotubes. Gel-spun PAN does not develop into a graphitic structure when carbonized at around 1200 ℃. However, as shown in fig. 12, gel-spun PAN/CNT containing about 1 wt.% CNTs showed a significant graphitic peak in the raman spectrum when subjected to this temperature and the same stress conditions. This graphitic peak is not due to the presence of CNTs, but rather due to the conversion of PAN to graphitic structure in the presence of CNTs. These graphitic fibrillar structures contribute to increased tensile strength and modulus.

In this example, very fine continuous PAN/CN precursor fibers were successfully processed by bicomponent and gel spinning. The subsequent stabilization and carbonization steps resulted in carbon fibers having an effective diameter of about 1 μm, an average tensile strength of about 4.5GPa (about 2.5N/tex) and an average tensile modulus of about 463GPa (about 257N/tex).

Embodiments of the present invention are not limited to the specific formulations, process steps, and materials disclosed herein because such formulations, process steps, and materials may vary somewhat. Furthermore, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting, as the scope of various embodiments of the present invention will be limited only by the appended claims. For example, the temperature, stress and time parameters may vary depending on the materials used.

Therefore, although embodiments have been disclosed in detail, with particular reference to exemplary embodiments, those skilled in the art will appreciate that various changes and modifications can be made within the scope defined in the appended claims. Thus, the scope of various embodiments of the present invention should not be limited by the embodiments discussed above, but should be defined by the following claims and their equivalents.

All patents and other references mentioned are incorporated by reference as if fully set forth herein.

Claims (189)

1. A method of making a carbon fiber, the method comprising:

extruding a solution of a first component and a solution of a second component through a bicomponent extrusion device to form a bicomponent polymer fiber comprising the first component and the second component; and

drawing the bicomponent polymer fibers to form drawn bicomponent polymer fibers;

wherein the first component comprises an acrylonitrile-containing polymer.

2. The method of claim 1, further comprising stabilizing the drawn bicomponent polymer fiber.

3. The method of any of the preceding claims, further comprising separating the first component from the second component of the drawn or stabilized bicomponent polymer fiber.

4. The method of any of the preceding claims, further comprising carbonizing the primary component of the bi-component polymer fiber.

5. The method of any of the preceding claims, further comprising graphitizing the carbonized primary component of the bi-component polymer fiber.

6. The method of claim 1, wherein the extruding comprises gel-extruding.

7. The method of claim 1, wherein the extruding comprises solution-extruding.

8. The method of claim 1, wherein the drawn bicomponent polymeric fiber has an average diameter of about 100nm to about 1 mm.

9. The method of claim 2, wherein the stabilizing comprises stabilizing the drawn polymer fiber under tension.

10. The method of claim 2, wherein the stabilizing comprises stabilizing the drawn polymer fiber in an oxidizing environment.

11. The method of claim 2, wherein the stabilizing comprises stabilizing the drawn polymer fiber at a temperature of about 200 ℃ to about 400 ℃ for less than or equal to about 36 hours.

12. The method of claim 3, wherein the separating comprises dissolving the second component from the drawn or stabilized bicomponent polymer fiber; sonicating the drawn or stabilized bicomponent polymer fiber to reduce any interfacial interactions between the first component and the second component; heating to melt the second component to leave the drawn or stabilized bicomponent polymer fiber; heating to burn off the second component to leave the drawn or stabilized bicomponent polymer fiber; or a combination of at least two of the foregoing.

13. The method of claim 3, wherein the separating and stabilizing occur simultaneously.

14. The method of claim 4, wherein the carbonizing comprises carbonizing the stabilized polymer fiber under tension.

15. The method of claim 4, wherein the carbonizing comprises carbonizing the stabilized polymer fiber in an inert environment.

16. The method of claim 4, wherein the carbonizing comprises carbonizing the stabilized polymer fiber at a temperature of about 500 ℃ to about 1800 ℃ for less than or equal to about 2 hours.

17. The method of claim 5, wherein the graphitizing comprises graphitizing the carbonized polymer fiber under tension.

18. The method of claim 5, wherein the graphitizing comprises graphitizing the carbonized polymer fiber in a non-nitrogen-containing inert environment.

19. The method of claim 5, wherein the graphitizing comprises graphitizing the carbonized polymer fiber at about 1800 degrees Celsius to about 2800 degrees Celsius for less than or equal to about 1 hour.

20. The method of claim 1, wherein the carbon fibers have an average diameter of about 10nm to about 10 μm.

21. A carbon fibre obtainable by the process of any one of the preceding claims.

22. A method of making a carbon fiber comprising:

contacting Carbon Nanotubes (CNTs) with a polymer comprising acrylonitrile to form a first component solution;

extruding the first component solution with a second component solution to form a bi-component polymer-CNT fiber precursor comprising a first component and a second component; and

drawing the bicomponent polymer-CNT fiber precursor to form a drawn bicomponent polymer-CNT fiber.

23. The method of claim 22, further comprising stabilizing the drawn bi-component polymer-CNT fiber.

24. The method of any of the preceding claims, further comprising separating the first component from the second component of the drawn or stabilized bi-component polymer-CNT fiber.

25. The method of any of the preceding claims, further comprising carbonizing the primary component of the bi-component polymer-CNT fiber.

26. The method of any of the preceding claims, further comprising graphitizing the carbonized primary component of the bi-component polymer-CNT fiber.

27. The method of claim 22, wherein the CNTs comprise single wall nanotubes, double wall nanotubes, triple wall nanotubes, or a combination comprising two or more of the foregoing types of CNTs.

28. The method of claim 22, wherein the CNTs have an average diameter from about 0.5nm to about 25 nm.

29. The method of claim 22, wherein the CNTs have an average diameter less than or equal to about 10 nm.

30. The method of claim 22, wherein the CNTs have an average length greater than or equal to about 10 nm.

31. The method of claim 22, wherein the CNTs comprise from about 0.001 wt% to about 40 wt% of the total weight of the bi-component polymer-CNT fiber precursor.

32. The method of claim 22, wherein the drawn polymer-CNT fiber has an average diameter of about 100nm to about 1 mm.

33. The method of claim 23, wherein the stabilizing comprises stabilizing the drawn polymer-CNT fiber under tension.

34. The method of claim 23, wherein the stabilizing comprises stabilizing the drawn polymer-CNT fiber in an oxidizing environment.

35. The method of claim 23, wherein the stabilizing comprises stabilizing the drawn polymer-CNT fiber at a temperature of about 200 ℃ to about 400 ℃ for less than or equal to about 36 hours.

36. The method of claim 24, wherein the separating comprises dissolving the second component from the drawn or stabilized bi-component polymer-CNT fiber; sonicating the drawn or stabilized bi-component polymer-CNT fiber to reduce any interfacial interactions between the first component and the second component; heating to melt the second component to leave the drawn or stabilized bi-component polymer-CNT fiber; heating to burn off the second component to leave the drawn or stabilized bi-component polymer-CNT fiber; or a combination of at least two of the foregoing.

37. The method of claim 24, wherein the separating and stabilizing occur simultaneously.

38. The method of claim 25, wherein the carbonizing comprises carbonizing the stabilized polymer-CNT fiber under tension.

39. The method of claim 25, wherein the carbonizing comprises carbonizing the stabilized polymer-CNT fiber in an inert environment.

40. The method of claim 25, wherein the carbonizing comprises carbonizing the stabilized polymer-CNT fiber at about 500 ℃ to about 1800 ℃ for less than or equal to about 2 hours.

41. The method of claim 26, wherein the graphitizing comprises graphitizing the carbonized polymer-CNT fiber under tension.

42. The method of claim 26, wherein the graphitizing comprises graphitizing the carbonized polymer-CNT fiber in a non-nitrogen-containing inert environment.

43. The method of claim 26, wherein the graphitizing comprises graphitizing the carbonized polymer-CNT fiber at about 1800 ℃ to about 2800 ℃ for less than or equal to about 1 hour.

44. The method of claim 22, wherein the carbon fibers have an average diameter of about 10nm to about 10 μm.

45. The method of claim 22, wherein the CNTs comprise from about 0.001 wt% to about 80 wt% of the total weight of the carbon fiber.

46. The method of claim 22, wherein the CNTs in the carbon fiber are exfoliated.

47. The method of claim 22, wherein the carbon fibers comprise microcrystalline graphitic regions radially extending about 0.34nm to about 50nm away from the wall of each CNT.

48. The method of claim 47, wherein the crystallized graphitic region extends radially at least about 2nm from the wall of each CNT.

49. The method of claim 22, wherein the carbon fiber has an electrical conductivity at least 25% greater than a carbon fiber without the CNT.

50. The method of claim 22, wherein the extruding comprises gel-extruding.

51. The method of claim 22, wherein the extruding comprises solution-extruding.

52. The method of claim 22, wherein the carbon fiber has a tensile strength at least 0.5GPa greater than a carbon fiber without the CNT.

53. The method of claim 22, wherein the carbon fiber has a tensile modulus at least 50GPa greater than a carbon fiber without the CNT.

54. A method of making a carbon thin film, comprising:

contacting Carbon Nanotubes (CNTs) with a polymer comprising acrylonitrile to form a first component solution;

extruding the first component solution and a second component solution to form a bi-component polymer-CNT film precursor comprising a first component and a second component; and

stretching the bi-component polymer-CNT film precursor to form a drawn bi-component polymer-CNT film.

55. The method of claim 54, further comprising stabilizing the drawn bi-component polymer-CNT film.

56. The method of any of the preceding claims, further comprising separating the first component from the second component of the drawn or stabilized bi-component polymer-CNT film.

57. The method of any of the preceding claims, further comprising carbonizing the primary component of the bi-component polymer-CNT film.

58. The method of any of the preceding claims, further comprising graphitizing the carbonized primary component of the bi-component polymer-CNT film.

59. The method of claim 54, wherein the CNTs comprise single-wall nanotubes, double-wall nanotubes, triple-wall nanotubes, or a combination comprising two or more of the foregoing types of CNTs.

60. The method of claim 54, wherein the CNTs have an average diameter from about 0.5nm to about 25 nm.

61. The method of claim 54, wherein the CNTs have an average diameter less than or equal to about 10 nm.

62. The method of claim 54, wherein the CNTs have an average length greater than or equal to about 10 nm.

63. The method of claim 54, wherein the CNTs comprise about 0.001 wt% to about 40 wt% of the total weight of the bi-component polymer-CNT film precursor.

64. The method of claim 54, wherein the drawn polymer-CNT film has an average thickness of about 50nm to about 50 μm.

65. The method of claim 55, wherein the stabilizing comprises stabilizing the drawn polymer-CNT film under tension.

66. The method of claim 55, wherein the stabilizing comprises stabilizing the drawn polymer-CNT film in an oxidizing environment.

67. The method of claim 55, wherein the stabilizing comprises stabilizing the drawn polymer-CNT film at a temperature of about 200 ℃ to about 400 ℃ for less than or equal to about 36 hours.

68. The method of claim 56, wherein the separating comprises dissolving the second component from the drawn or stabilized bi-component polymer-CNT film; sonicating the drawn or stabilized bi-component polymer-CNT film to reduce any interfacial interactions between the first component and the second component; heating to melt the second component to leave the drawn or stabilized bi-component polymer-CNT film; heating to burn off the second component to leave the drawn or stabilized bi-component polymer-CNT film; or a combination of at least two of the foregoing.

69. The method of claim 56, wherein the separating and stabilizing occur simultaneously.

70. The method of claim 57, wherein the carbonizing comprises carbonizing the stabilized polymer-CNT film under tension.

71. The method of claim 57, wherein the carbonizing comprises carbonizing the stabilized polymer-CNT film in an inert environment.

72. The method of claim 57, wherein the carbonizing comprises carbonizing the stabilized polymer-CNT fiber at about 500 ℃ to about 1800 ℃ for less than or equal to about 2 hours.

73. The method of claim 58, wherein the graphitizing comprises graphitizing the carbonized polymer-CNT film under tension.

74. The method of claim 58, wherein the graphitizing comprises graphitizing the carbonized polymer-CNT film in a non-nitrogen-containing inert environment.

75. The method of claim 58, wherein the graphitizing comprises graphitizing the carbonized polymer-CNT film at about 1800 degrees Celsius to about 2800 degrees Celsius for less than or equal to about 1 hour.

76. The method of claim 54, wherein the carbon film has an average thickness of about 25nm to about 25 μm.

77. The method of claim 54, wherein the CNTs comprise about 0.001 wt% to about 80 wt% of the total weight of the carbon film.

78. The method of claim 54, wherein the CNTs within the carbon film are exfoliated.

79. The method of claim 54, wherein the carbon film comprises a region of microcrystalline graphite extending radially from about 0.34nm to about 50nm away from a wall of each CNT.

80. The method of claim 80, wherein the crystallized graphitic region extends radially at least about 2nm from the wall of each CNT.

81. The method of claim 54, wherein the carbon film has an electrical conductivity at least 25% greater than an electrical conductivity of a carbon film without CNTs.

82. The method of claim 54, wherein the extruding comprises gel-extruding.

83. The method of claim 54, wherein the extruding comprises solution-extruding.

84. The method of claim 54, wherein the carbon film has a tensile strength at least 0.5GPa greater than a tensile strength of a carbon film without the CNT.

85. The method of claim 54, wherein the carbon film has a tensile modulus at least 50GPa greater than a tensile modulus of a carbon film without the CNT.

86. A method of making a carbon fiber comprising:

contacting graphite flakes with a polymer comprising acrylonitrile to form a first component solution;

extruding the first component solution with a second component solution to form a bi-component polymer-graphite sheet fiber precursor comprising a first component and a second component; and

drawing the bi-component polymer-graphite sheet fiber precursor to form a drawn polymer-graphite sheet fiber.

87. The method of claim 86, further comprising stabilizing the drawn bi-component polymer-graphite sheet fiber.

88. The method of any of the preceding claims, further comprising separating the first component from the second component of the drawn or stabilized bi-component polymer-graphite sheet fiber.

89. The method of any of the preceding claims, further comprising carbonizing the primary component of the bi-component polymer-graphite sheet fiber.

90. The method of any of the preceding claims, further comprising graphitizing the carbonized primary component of the bi-component polymer-graphite sheet fiber.

91. The method of claim 86, wherein the graphite sheets have an average width of about 0.5nm to about 100 nm.

92. The method of claim 86, wherein the graphite sheets have an average thickness of about 0.5nm to about 25 nm.

93. The method of claim 86, wherein the graphite sheets have an average width of less than or equal to about 10 nm.

94. The method of claim 86, wherein the graphite sheets have an average length of greater than or equal to about 10 nm.

95. The method of claim 86, wherein the graphite sheets comprise about 0.001 weight percent to about 40 weight percent of the bi-component polymer-graphite sheet fiber precursor, based on a total weight of the bi-component polymer-graphite sheet fiber precursor.

96. The method of claim 86, wherein the drawn polymer-graphite sheet fiber has an average diameter of about 100nm to about 1 mm.

97. The method of claim 87, wherein the stabilizing comprises stabilizing the drawn polymer-graphite sheet fiber under tension.

98. The method of claim 87, wherein the stabilizing comprises stabilizing the drawn polymer-graphite sheet fiber in an oxidizing environment.

99. The method of claim 87, wherein the stabilizing comprises stabilizing the drawn polymer-graphite sheet fiber at a temperature of about 200 ℃ to about 400 ℃ for less than or equal to about 36 hours.

100. The method of claim 88, wherein the separating comprises dissolving the second component from the drawn or stabilized bi-component polymer-graphite sheet fiber; sonicating the drawn or stabilized bi-component polymer-graphite sheet fiber to reduce any interfacial interactions between the first component and the second component; heating to melt the second component to leave the drawn or stabilized bi-component polymer-graphite sheet fiber; heating to burn off the second component to leave the drawn or stabilized bi-component polymer-graphite sheet fiber; or a combination of at least two of the foregoing.

101. The method of claim 88, wherein the separating and stabilizing occur simultaneously.

102. The method of claim 89, wherein the carbonizing comprises carbonizing the stabilized polymer-graphite sheet fiber under tension.

103. The method of claim 89, wherein the carbonizing comprises carbonizing the stabilized polymer-graphite sheet fiber in an inert environment.

104. The method of claim 89, wherein the carbonizing comprises carbonizing the stabilized polymer-graphite sheet fiber at about 500 ℃ to about 1800 ℃ for less than or equal to about 2 hours.

105. The method of claim 90, wherein the graphitizing comprises carbonizing the carbonized polymer-graphite sheet fiber under tension.

106. The method of claim 90, wherein the graphitizing comprises graphitizing the carbonized polymer-graphite sheet fiber in a non-nitrogen-containing inert environment.

107. The method of claim 90, wherein the graphitizing comprises graphitizing the carbonized polymer-graphite sheet fiber at about 1800 degrees Celsius to about 2800 degrees Celsius for less than or equal to about 1 hour.

108. The method of claim 86, wherein the carbon fibers have an average diameter of about 10nm to about 10 μm.

109. The method of claim 86, wherein the graphite sheets comprise about 0.001 weight percent to about 80 weight percent of the carbon fiber, based on the total weight of the carbon fiber.

110. The method of claim 86, wherein the graphite sheets in the carbon fibers are exfoliated.

111. The method of claim 86, wherein the carbon fibers comprise microcrystalline graphitic regions radially extending about 0.34nm to about 50nm from the face of each graphite sheet.

112. The method of claim 111, wherein the crystallized graphitic region extends radially at least about 2nm from the face of each graphite sheet.

113. The method of claim 86, wherein the carbon fiber has an electrical conductivity at least 25% greater than the electrical conductivity of a carbon fiber without graphite sheets.

114. The method of claim 86, wherein the extruding comprises gel-extruding.

115. The method of claim 86, wherein the extruding comprises solution-extruding.

116. The method of claim 86, wherein the carbon fiber has a tensile strength at least 0.5GPa greater than a carbon fiber without the graphite sheets.

117. The method of claim 86, wherein the carbon fiber has a tensile modulus at least 50GPa greater than a carbon fiber without the graphite sheets.

118. A method of making a carbon thin film, comprising:

contacting graphite flakes with a polymer comprising acrylonitrile to form a first component solution;

extruding the first component solution with a second component solution to form a bi-component polymer-graphite sheet film precursor comprising a first component and a second component; and

stretching the bi-component polymer-graphite sheet film precursor to form a drawn polymer-graphite sheet film.

119. The method of claim 118, further comprising stabilizing the drawn bi-component polymer-graphite sheet film.

120. The method of any of the preceding claims, further comprising separating the first component from the second component of the drawn or stabilized bi-component polymer-graphite sheet film.

121. The method of any of the preceding claims, further comprising carbonizing the primary component of the bi-component polymer-graphite sheet film.

122. The method of any of the preceding claims, further comprising graphitizing the carbonized primary component of the bi-component polymer-graphite sheet film.

123. The method of claim 118, wherein the graphite sheets have an average width of about 0.5nm to about 100 nm.

124. The method of claim 118, wherein the graphite sheets have an average thickness of about 0.5nm to about 25 nm.

125. The method of claim 118, wherein the graphite sheets have an average width of less than or equal to about 10 nm.

126. The method of claim 118, wherein the graphite sheets have an average length of greater than or equal to about 10 nm.

127. The method of claim 118, wherein the graphite sheets comprise about 0.001 weight percent to about 40 weight percent of the bi-component polymer-graphite sheet fiber precursor, based on a total weight of the bi-component polymer-graphite sheet fiber precursor.

128. The method of claim 118, wherein the drawn polymer-graphite sheet thin ink has an average thickness of about 50nm to about 50 μ ι η.

129. The method of claim 119, wherein the stabilizing comprises stabilizing the drawn polymer-graphite sheet film under tension.

130. The method of claim 119, wherein the stabilizing comprises stabilizing the drawn polymer-graphite sheet film in an oxidizing environment.

131. The method of claim 119, wherein the stabilizing comprises stabilizing the drawn polymer-graphite sheet film at a temperature of about 200 ℃ to about 400 ℃ for less than or equal to about 36 hours.

132. The method of claim 120, wherein the separating comprises dissolving the second component from the drawn or stabilized bi-component polymer-graphite sheet film; sonicating the drawn or stabilized bi-component polymer-graphite sheet film to reduce any interfacial interactions between the first component and the second component; heating to melt the second component to leave the drawn or stabilized bi-component polymer-graphite sheet film; heating to burn off the second component to leave the drawn or stabilized bi-component polymer-graphite sheet film; or a combination of at least two of the foregoing.

133. The method of claim 120, wherein the separating and stabilizing occur simultaneously.

134. The method of claim 121, wherein the carbonizing comprises carbonizing the stabilized polymer-graphite sheet film under tension.

135. The method of claim 121, wherein the carbonizing comprises carbonizing the stabilized polymer-graphite sheet film in an inert environment.

136. The method of claim 121, wherein the carbonizing comprises carbonizing the stabilized polymer-graphite sheet film at about 500 ℃ to about 1800 ℃ for less than or equal to about 2 hours.

137. The method of claim 122, wherein the graphitizing comprises graphitizing the carbonized polymer-graphite sheet fiber under tension.

138. The method of claim 122, wherein the graphitizing comprises graphitizing the carbonized polymer-graphite sheet film in a non-nitrogen-containing inert environment.

139. The method of claim 122, wherein the graphitizing comprises graphitizing the carbonized polymer-graphite sheet film at about 1800 degrees celsius to about 2800 degrees celsius for less than or equal to about 1 hour.

140. The method of claim 118, wherein the carbon film has an average thickness of about 25nm to about 25 μ ι η.

141. The method of claim 118, wherein the graphite sheets comprise about 0.001 wt% to about 80 wt% of the total weight of the carbon film.

142. The method of claim 118, wherein the graphite sheets in the carbon film are exfoliated.

143. The method of claim 118, wherein the carbon film comprises a microcrystalline graphitic region radially extending about 0.34nm to about 50nm from a face of each graphite sheet.

144. The method of claim 143, wherein the crystallized graphitic region extends radially at least about 2nm from the face of each graphite sheet.

145. The method of claim 118, wherein the carbon film has an electrical conductivity at least 25% greater than the electrical conductivity of a carbon film without graphite sheets.

146. The method of claim 118, wherein the extruding comprises gel-extruding.

147. The method of claim 118, wherein the extruding comprises solution-extruding.

148. The method of claim 118, wherein the carbon film has a tensile strength at least 0.5GPa greater than a carbon film formed without the graphite sheets.

149. The method of claim 118, wherein the carbon film has a tensile modulus at least 50GPa greater than a carbon film formed without the graphite sheets.

150. A carbon fiber formed from Carbon Nanotubes (CNTs) and an acrylonitrile-containing polymer, the carbon fiber having:

an average diameter of about 10nm to about 10 μm; and

a region of microcrystalline graphite extending radially from about 0.34nm to about 50nm from the wall of each CNT.

151. The carbon fiber of claim 150, wherein the region of microcrystalline graphite extends radially away from the wall of each CNT by at least about 2 nm.

152. The carbon fiber of claim 150, wherein the carbon fiber has an average diameter of less than or equal to about 500 nm.

153. The carbon fiber of claim 150, wherein the CNTs have an average diameter from about 0.5nm to about 25 nm.

154. The carbon fiber of claim 150, wherein the CNTs have an average diameter less than or equal to about 10 nm.

155. The carbon fiber of claim 150, wherein the CNTs in the carbon fiber are exfoliated.

156. The carbon fiber of claim 150, wherein the carbon fiber has an electrical conductivity that is at least 25% greater than the electrical conductivity of a carbon fiber without the CNT.

157. The carbon fiber of claim 150, wherein the carbon fiber has a tensile strength at least about 0.65GPa greater than a carbon fiber formed without the CNT.

158. The carbon fiber of claim 150, wherein the carbon fiber has a tensile modulus at least about 75GPa greater than a carbon fiber formed without the CNT.

159. The carbon fiber of claim 150, wherein the carbon fiber is optically transparent.

160. A carbon thin film formed of Carbon Nanotubes (CNTs) and an acrylonitrile-containing polymer, the carbon thin film having:

an average thickness of about 25nm to about 25 μm; and

a region of microcrystalline graphite extending radially from about 0.34nm to about 50nm from the wall of each CNT.

161. The carbon film of claim 160, wherein the microcrystalline graphitic region radially extends at least about 2nm away from the wall of each CNT.

162. The carbon film of claim 160, wherein the carbon film has an average thickness of less than or equal to about 1 μ ι η.

163. The carbon film of claim 160, wherein the CNTs have an average diameter from about 0.5nm to about 25 nm.

164. The carbon film of claim 160, wherein the CNTs have an average diameter less than or equal to about 10 nm.

165. The carbon film of claim 160, wherein the CNTs in the carbon film are exfoliated.

166. The carbon film of claim 160, wherein the carbon film has an electrical conductivity at least 25% greater than an electrical conductivity of a carbon film without the CNTs.

167. The carbon film of claim 160, wherein the carbon film has a tensile strength at least about 0.65GPa greater than a carbon film formed without the CNT.

168. The carbon film of claim 160, wherein the carbon film has a tensile modulus at least about 75GPa greater than a carbon film formed without the CNT.

169. The carbon film of claim 160, wherein the carbon film is optically transparent.

170. A carbon fiber formed from a graphite sheet and an acrylonitrile-containing polymer, the carbon fiber having:

an average diameter of about 10nm to about 10 μm; and

a region of microcrystalline graphite extending radially from about 0.34nm to about 50nm from the face of each graphite sheet.

171. The carbon fiber of claim 170, wherein the microcrystalline graphitic region extends radially at least about 2nm from the face of each graphite sheet.

172. The carbon fiber of claim 170, wherein the carbon fiber has an average diameter of less than or equal to about 500 nm.

173. The carbon fiber of claim 170, wherein the graphite sheets have an average width of from about 0.5nm to about 100 nm.

174. The carbon fiber of claim 170, wherein the graphite sheets have an average thickness of about 0.5nm to about 25 nm.

175. The carbon fiber of claim 170, wherein the graphite sheets in the carbon fiber are exfoliated.

176. The carbon fiber of claim 170, wherein the carbon fiber has an electrical conductivity that is at least 25% greater than the electrical conductivity of a carbon fiber comprising no graphite sheets.

177. The carbon fiber of claim 170, wherein the carbon fiber has a tensile strength at least about 0.65GPa greater than a carbon fiber formed without the graphite sheets.

178. The carbon fiber of claim 170, wherein the carbon fiber has a tensile modulus at least about 75GPa greater than a carbon fiber formed without the graphite sheets.

179. The carbon fiber of claim 170, wherein the carbon fiber is optically transparent.

180. A carbon film formed from a graphite sheet and an acrylonitrile-containing polymer, the carbon film having:

an average thickness of about 25nm to about 25 μm; and

a region of microcrystalline graphite extending radially from about 0.34nm to about 50nm from the wall of each graphite sheet.

181. The carbon film of claim 180, wherein the microcrystalline graphitic region radially extends at least about 2nm from the face of each graphite sheet.

182. The carbon film of claim 180, wherein the carbon film has an average thickness of less than or equal to about 1 μm.

183. The carbon film of claim 180, wherein the graphite sheets have an average width of about 0.5nm to about 100 nm.

184. The carbon film of claim 180, wherein the graphite sheets have an average thickness of about 0.5nm to about 25 nm.

185. The carbon film of claim 180, wherein the graphite sheets in the carbon film are exfoliated.

186. The carbon film of claim 180, wherein the carbon film has an electrical conductivity at least 25% greater than the electrical conductivity of a carbon film comprising no graphite sheets.

187. The carbon film of claim 180, wherein the carbon film has a tensile strength at least about 0.65GPa greater than a carbon film formed without the graphite sheets.

188. The carbon film of claim 180, wherein the carbon film has a tensile modulus at least about 75GPa greater than a carbon film formed without the graphite sheets.

189. The carbon film of claim 180, wherein the carbon film is optically transparent.